In a tree bark, promise of sleep apnoea cure

OBSTRUCTIVE SLEEP apnoea, which causes people to briefly stop breathing while asleep, affects an estimated 5% of the population, not including the many more who don’t even realise they suffer from the disorder.

Patients are sometimes treated with a machine that blows air into their airways through a face mask, but no drug treatments exist. In an advance that may change that, MIT researchers have discovered that a dietary supplement called yohimbine reverses the root cause of obstructive sleep apnoea in an animal model.

Yohimbine, a chemical derived from the bark of the African yohimbe tree, has a long history of use by humans as an aphrodisiac, and more recently it has been used by bodybuilders to burn fat. It is not Fda-approved for any of these uses, however. Chi-sang Poon, a principal research scientist at MIT’S Institute for Medical Engineering and Science (IMES), says that while the results of the obstructive sleep apnoea study are promising, people should not begin taking the drug on their own, especially those who also suffer from heart disease, high blood pressure, or anxiety disorders.

Obstructive sleep apnoea is caused by a narrowing of the airway that cuts off breathing, and people who are obese are at higher risk for the disorder. This closing of the airway often occurs during sleep, especially REM sleep, when most of the body’s muscles are relaxed, including the tongue. If the tongue falls back into an already narrow airway, it can cut off the flow of air.

Previous research had suggested that the hypoglossal neurons that control the tongue are stimulated by a part of the brain known as the pons, located in the brain stem. Two particular groups of neurons in the pons, known as A5 and A7, had been thought to contribute to hypoglossal neuron activation. In experiments performed on rats, the researchers found that obstructive apnoea that is artificially imposed while the animals are not asleep can actually make this A5 and A7 activation of hypoglossal neurons become even stronger, and stay strong long afterward.

But the activity of A5 and A7 usually drops dramatically during sleep, especially REM sleep. The researchers sought to find a way to re-activate these neuron groups, and found that yohimbine treatment stimulated the hypoglossal neurons and restored their vigilance against obstructive sleep apnoea in rats. (EDITED EXCERPTS FROM MIT NEWS)